1. Field of the Invention
The present invention relates to a paper feeder device for miniaturized printers and, more particularly, to a paper feeder device for feeding paper while intermittently rotating a paper feed roller by the driving force of an electromagnetic plunger.
2. Description of the Prior Art
Miniaturized printers have become popular in recent years and are being mounted in portable electronic desk calculators. A greater part of this kind of miniaturized printers employ a paper feed mechanism using an electromagnetic plunger.
There are U.S. Pat. No. 4,133,422 and U.S. Pat. No. 4,051,942 which are directed to the above-mentioned kind of printers and which are based on patent applications filed on behalf of the assignee of the present invention.
Although the paper feed mechanisms mentioned above can be assembled easily at a low cost, a voltage supplied to the electromagnetic plunger varies so that the paper cannot be fed stably.
In a conventional paper feed mechanism as shown in FIG. 1, a pawl 22 of a lever operatively connected to an operation rod of an electromagnetic plunger is moved in the direction of the arrow to rotate a ratchet wheel 21 in the same direction at one pitch angle, which ratchet wheel 21 is mounted on a drive shaft 20 having a paper feed roller fixedly mounted thereon. When a voltage supplied to the electromagnetic plunger varies, the ratchet wheel 21 is rotated at more than one pitch angle by the inertia force. This sometimes causes an engement pawl 23, which is repeatedly engaged with and disengaged from a recess between two adjacent teeth of the ratchet 21, and which is resiliently pressed by a spring, to pass off a predetermined engagement position or stop the ratchet wheel 21 in a position where the ratchet wheel 21 has been rotated at two or more pitch angles.
An excessive paper feed caused by such an excessive rotation of the ratchet wheel as mentioned above is called "paper skip". This causes a broken file so that the quality of typewritten data is greatly decreased.